Doctors serve risky arthritis cocktail

Doctors are putting patients at risk of serious kidney complications by prescribing a dangerous mix of new arthritis medications and blood pressure drugs, research has found.

Between 5 and 8 per cent of patients taking the popular drugs, such as Celebrex and Vioxx, to control osteoarthritis pain, were also taking an ACE inhibitor and a diuretic to control blood pressure, according to a nationwide survey of more than 3500 patients and 400 GP practices. Doctors are specifically warned against this combination of drugs.

As well, up to one-third of the patients on the new arthritis drugs, known as COX-2 inhibitors, were taking them at the same time as blood pressure medications - less risky than using all three at once but still not safe.

Study leader Stephen Kerr, from the National Prescribing Service, said doctors appeared to have been lulled into a false sense of security about the COX-2 drugs, after advertising campaigns that following their listing three years ago on the Pharmaceutical Benefits Scheme.

"Intense drug promotion can create perceptions about medicines that strongly influence patterns of prescribing and use, yet may not be in line with best available evidence," wrote Dr Kerr in this week's Medical Journal of Australia.

Doctors increased patients' risk of falling victim to drug side-effects whenever they prescribed new medicines soon after their release. This was because many adverse reactions, particularly "idiosyncratic" reactions that were not obviously related to the drug's chemical properties, did not become apparent until the drug was in widespread use, wrote Dr Kerr.

The chairman of the therapeutics committee of the Australian Rheumatology Association, Jim Bertouch, said combining COX-2 inhibitors with diuretics and ACE inhibitors was a "triple whammy . . . I don't think anyone would dispute that's a concern."

He said the COX-2 drugs carried a lower risk of triggering gastrointestinal bleeding than non-steroidal anti-inflammatory drugs (NSAIDs) - previously the main treatment for arthritis pain. But their potential effect on the kidneys was exactly the same as for NSAIDs.

Dr Bertouch, who is also chairman of rheumatology at Prince of Wales Hospital, said the level of risky prescribing was unacceptably high - particularly because doctors had been specifically warned against this combination when the COX-2 inhibitors were launched.

A new education campaign might be needed to ensure doctors got the message, he said: "Despite the fact that we, and others, have tried to draw attention to this, obviously the message has not got through. We probably need to do more."

The kidney side-effects, which could include total kidney failure or the worsening of existing kidney conditions, predominantly affected patients aged 60 or older, whose kidney function was likely to be less than perfect, Dr Bertouch said.

Such patients should be carefully monitored for signs of fluid retention, such as high blood pressure and swelling of the feet and hands, and should also have a full kidney function test from time to time.